Field of the Invention
This invention relates generally to a combustion basket assembly for a gas turbine engine, where the assembly includes a double-wall exit cone and a splash plate at an output end of the combustion basket and, more particularly, to a combustion basket assembly for a gas turbine engine, where the assembly includes a double-wall exit cone and a splash plate at an output end of the combustion basket, and where an array of pairs of cooling feed holes are provided that separately provide cooling air to the exit cone and the splash plate.
Discussion of the Related Art
The world's energy needs continue to rise which provides a demand for reliable, affordable, efficient and environmentally-compatible power generation. A gas turbine engine is one known machine that provides efficient power, and often has application for an electric generator in a power plant, or engines in an aircraft or a ship. A typical gas turbine engine includes a compressor section, a combustion section and a turbine section. The compressor section provides a compressed airflow to the combustion section where the air is mixed with a fuel, such as natural gas. The combustion section includes a plurality of circumferentially disposed combustors that receive the fuel to be mixed with the air and ignited to generate a working gas. The working gas expands through the turbine section and is directed across rows of blades therein by associated vanes. As the working gas passes through the turbine section, it causes the blades to rotate, which in turn causes a shaft to rotate, thereby providing mechanical work.
The temperature of the working gas is tightly controlled so that it does not exceed some predetermined temperature for a particular turbine engine design because too high of a temperature can damage various parts and components in the turbine section of the engine. However, it is desirable to cause the temperature of the working gas to be as high as possible because the higher the temperature of the working gas, the faster the flow of the gas, which results in a more efficient operation of the engine.
In certain gas engine turbine designs, a portion of the compressed airflow is also used to provide cooling for certain components in the turbine section, such as the vanes, blades and ring segments. The more cooling and/or the more efficient cooling that can be provided to these components allows the components to be maintained at a lower temperature, and thus the higher the temperature the working gas can be. For example, by reducing the temperature of the compressed air, less compressed air is required to maintain the part at the desired temperature, resulting in a higher working gas temperature and a greater power and efficiency from the engine. Further, by using less cooling air at one location in the turbine section, more cooling air can be used at another location in the turbine section. In one known turbine engine design, 80% of the compressed airflow is mixed with the fuel to provide the working gas and 20% of the compressed airflow is used to cool the turbine parts. If less of that cooling air is used at one particular location as a result of the cooling air being lower in temperature, then more cooling air can be used at other areas for increased cooling.
In one known gas turbine engine design, a combustor basket is provided in each combustor of the engine, where the fuel and air are mixed together and ignited to generate a hot working gas. The hot working gas from the combustor basket flows into a transition component and is directed to the first row of vanes in the engine. It has been shown that some of the hot working gas that exits the combustor basket is caused to flow in a reverse direction and be directed towards an exit cone of the combustor basket, which sometimes causes burning of a downstream surface of the exit cone and a basket liner. It is known in the art to provide a splash plate between a single wall exit cone and the basket liner at the end of the combustion basket that prevents the hot working gas from directly impinging and burning the basket liner. The splash plate provides backside cooling to both the inner diameter surface and outer diameter surface of the basket, which allows both surfaces to be coated with a thermal barrier coating. Cooling flow is provided to the backside surface of the exit cone through cooling holes in the basket liner. However, the single wall exit cone still experiences heating distress. Particularly, the cooling air supply provided to the cooling holes in the basket liner is split between the splash plate and the exit cone, where the splash plate typically receives the majority of the cooling air. It is difficult to control the separation of the cooling air to the exit cone and the splash plate, where the exit cone could receive reduced cooling and increased distress.